Английская Википедия:Actinocene
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Actinocenes are a family of organoactinide compounds consisting of metallocenes containing elements from the actinide series. They typically have a sandwich structure with two dianionic cyclooctatetraenyl ligands (COT2-, which is Шаблон:Chem) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C8H8)2.[1][2]
Characterised actinocenes
| Name | Formula | AnIV centre | First synthesis | Crystal colour | An–COT distance (Å) | Space group |
|---|---|---|---|---|---|---|
| Thorocene | Th(C8H8)2 | Th | 1969 | bright yellow | 2.004 | P21/n |
| Protactinocene | Pa(C8H8)2 | Pa | 1974 | yellowish | – | P21/n |
| Uranocene | U(C8H8)2 | U | 1968 | deep green | 1.926 | P21/n |
| Neptunocene | Np(C8H8)2 | Np | 1970 | yellow-brown | 1.909 | P21/n |
| Plutonocene | Pu(C8H8)2 | Pu | 1970 | dark red | 1.898 | I2/m |
The most studied actinocene is uranocene, U(C8H8)2, which in 1968 was the first member of this family to be synthesised and is still viewed as the archetypal example.[2][3] Other actinocenes that have been synthesised are protactinocene[4] (Pa(C8H8)2), thorocene[5] (Th(C8H8)2), neptunocene[6] (Np(C8H8)2), and plutonocene[7][8] (Pu(C8H8)2). Especially the latter two, neptunocene and plutonocene, have not been extensively studied experimentally since the 1980s because of the radiation hazard they pose.[7][8]
Bonding
The actinide-cyclooctatetraenyl bonding has been of interest for multiple theoretical studies.[8][9] Computational chemistry methods indicate bonding with a large covalent character resulting mainly from the mixing of actinide 6d orbitals with ligand π-orbitals, with a smaller interaction involving the actinide 5f and ligand π-orbitals.[9] The covalent component is characterised by donation of electron density to the actinide.
Analogous sandwiched M(C8H8)2 compounds also exist for lanthanides M = Nd, Tb, and Yb, but therein the bonding is mostly ionic rather than covalent (see lanthanocenes).[3]
See also
References
